Multi-axis force sensor

Active Publication Date: 2020-02-13
KING'S COLLEGE LONDON
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

This patent describes structures for force sensors that are compact and easy to make. They use stacked ring sensor elements that are connected by resiliently mounted connection bars. These bars can be positioned in the same plane as the rings, reducing sensitivity to torque, or they can be positioned obliquely between the rings, providing sensitivity to torque and making the sensor a five-axis sensor. The directional component of the connection bars can be adjusted to provide sensitivity to torque about the axis. The shapes of the rings can be circular, square, triangular, or polyynchronous. The invention allows for a compact and versatile force sensor design.

Problems solved by technology

Multi-axis force sensors that measure multiple degrees of freedom (DoF) are known already, but often take complicated and expensive forms.
In order to measure all six degrees of freedom previously, it has been necessary to combine multiple 2 or 3 DoF sensors together, usually by having to over-provision the number of sensors, such that overall cost of the resulting sensor is high.

Method used

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Experimental program
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first embodiment

[0050]The physical structure of the force sensor is shown in FIGS. 1 to 17. From these figures it will be seen that the sensor comprises a circular upper element 100 and a circular lower element 200, both of which are identical to each other. Each element in turn comprises an upper ring 108, 208, and a lower ring 110, 210, with the lower ring 110 of the upper element 100 being mounted on the upper ring 208 of the lower element, such that the elements 100 and 200 can be considered stacked on top of each other. The upper and lower rings lie with their circumferences in the X-Y plane of the sensor, with the Z-axis running along the axis of rings orthogonal to the X-Y plane.

[0051]Within each element 100 and 200 are formed three respective beam structures that extend circumferentially around the rings, and connect the respective upper rings and the lower rings of each element. Each beam structure comprises two elongated Z-shaped beams, with the long axis 102, 104, 202, 204 of each beam ...

second embodiment

[0070]Regarding how six-axis force measurements may be obtained from the sensor of the second embodiment, the derivation of the signal processing described to obtain the measurements from the optical displacement measurements made from the optical sensors is described next with respect to FIGS. 38 to 40.

[0071]With reference to FIGS. 38 and 39, the sensor structure has six s shaped beams, from their deflections (δ1, δ2, δ3 δ4, δ5, and δ6), the force components (f1, f2, f3, f4, f5, and f6) can be calculated by multiplying the six deflections by spring coefficients k as shown in Equations. 2.1 to 2.6.

f1=k1δ1  (2.1)

f2=k2δ2  (2.2)

f3=k3δ3  (2.3)

f4=k4δ4  (2.4)

f5=k5δ5  (2.5)

f6=k6δ6  (2.6)

[0072]From these six force components, Fz, M1x, M2x, M1y, M2y, Mx, and My can be calculated using Equations 7 to 12.

Fz=(f1+f2+f3+f4+f5+f6) / 2  (2.7)

Mx=M2x−M1x,My=M2y−M1y  (2.8)

M1x=−L2y·f5+L1y·f6+L3y·f4  (2.9)

M1y=L1x·f6−L3x·f4  (2.10)

M2x=−L2y·f2+L1y·f3+L3y·f1  (2.11)

M2y=L1x·f3−L3x·f1  12)

Mx=L3y·f1−L2y·f2+L1y·...

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Abstract

Embodiments of the invention provide structures for a force sensor, and force sensors using such structures, which are compact and easy to manufacture, for example by 3D printing. In particular the structures comprise a pair of stacked ring sensor elements, the ring sensor elements in turn being formed by upper and lower ring elements joined together at points around the circumference thereof by resiliently mounted connection bars. The connection bars may extend in the same plane as the rings, in which case sensitivity to torque about the axis of the rings is much reduced, such that a five-axis sensor is effectively obtained, or the connection bars may extend obliquely between the upper and lower rings of each sensor element, such that they have a directional component in the direction of the axis of the rings (the rings of each element being co-axially stacked). In this second case application of a torque about the ring axis causes the oblique connection bars to either increase or decrease their directional component in the axial direction, thus providing sensitivity to torque about the axis, and providing a compact six axis sensor.

Description

TECHNICAL FIELD[0001]Embodiments of the present invention relate to a multi-axis force sensor, and in particular to a sensor that is able to provide force sensing in at least five degrees of freedom (DoF).BACKGROUND TO THE INVENTION AND PRIOR ART[0002]Multi-axis force sensors that measure multiple degrees of freedom (DoF) are known already, but often take complicated and expensive forms. In a three dimensional Cartesian co-ordinate space there are up to six degrees of freedom that can be measured, being linear force F in each of the x, y, and z directions (i.e. Fx, Fy, and Fz), and also turning moment M about each of the x, y, and z axes (i.e. Mx, My, and Mz). In order to measure all six degrees of freedom previously, it has been necessary to combine multiple 2 or 3 DoF sensors together, usually by having to over-provision the number of sensors, such that overall cost of the resulting sensor is high.[0003]For example, Optoforce, of Budapest, Hungary, provide a three-axis force senso...

Claims

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Application Information

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IPC IPC(8): G01L5/16
CPCG01L5/166G01L5/009G01L1/00G01L1/048
InventorNOH, YOHANBIMBO, JOAORHODE, KAWALALTHOEFER, KASPARLIU, HONGBINHOUSDEN, RICHARD JAMESWURDEMANN, HELGE
OwnerKING'S COLLEGE LONDON